Electronic Measurement & Instrumentation

What is absolute and secondary instruments ?

What is recording and integrating instruments ?

State Blodel's Theorem for N-phase P-wire system.

What is difference between CT and PT ?

Give the classification of Resistance.

Write down the three methods for measuring the medium resistance.

What are interrupters and alternators.

Write down the three characteristics of detectors used in AC-bridge.

What is the difference between the AC and DC potentiometers.

What is the difference between polar-type potentiometers and co-ordinate type potentiometers.

The inductance of a moving iron ammeter in micro-henry is given by the expression. $$L=20+10\theta -3{\theta }^2$$ Where $\theta$ is the deflection in radians from zero position. Determine the deflection of ammeter for a current of $10\text{ A}$ if the spring constant is $8\times 10^{-6}\text{ Nm/radian}$.

Explain the working principle of a moving iron indicating instrument. Show that this type of instrument can be used both for dc and ac measurements.

Explain 3-voltmeter method for power measurement with the circuit and phasor diagram.

Explain the Hey's bridge for measurement of inductance with suitable phasor diagram.

Show that the Wein frequency bridge will be balanced at only one frequency given by : $$f=\frac{1}{2\pi \sqrt{R_1{R}_2{C}_1{C}_2}}$$ Where $C_1,C_2,R_1,$ and $R_2$ have their usual meanings.

Draw the construction and working of a dc potentiometer.

Explain the principle of a rectangular type co-ordinate a.c. potentiometer.

Calculate the inductance of a coil from the following measurements on an ac potentiometer. Voltage drop across a $0.3\Omega$ standard resistance connected in series with the coil $=0.612\angle 12^{\circ }\text{ V}$ Voltage across the test coil through $100/1$ volt ratio box $=0.781\angle 50^{\circ }48^{\prime }\text{ V}$ Frequency of supply is $50\text{ Hz}$.

Explain the construction of a PMMC meter with the help of a neat sketch. Derive the expression for deflection for a PMMC ammeter if it is (i) spring control and (ii) gravity control.

Draw the connection diagram of a $3\text{-}\varphi$ energy meter and explain its working. How do you correct it if it is found to be moving fast.

Describe Kelvin's double bridge for the comparison of two low resistances. Give the theory of the bridge and arrangement necessary in order that the greatest precision possible may be obtained.

State the various methods for measurement of low resistance. Why is the voltmeter-ammeter method unsuitable for the precise measurement of low resistance ?